Photographic elements are often composed of many layers of photosensitive and non-photosensitive materials, with each layer making a unique contribution to achieve a high degree of image quality. In color photography especially, the number of emulsion-applied layers is often considerable, with, in addition to one or more layers being deposited to define the proper level for each of the primary colors, layers being present that are responsible for performing antihalation, filtering, barrier, antistatic, and antiblocking functions. These layers function more or less independently, and it is important that the various components of the layers not migrate into neighboring layers. If migration occurs, the loss of the component not only diminishes overall performance of the function for which it was intended, but the migrated component also can interfere with the function of neighboring layers into which it has migrated. Migration is a serious problem in photography.
The [3H]-thiazole-2-thione heterocycle (I), ##STR1## also referred to as a [3H]-thiazoline-2-thione and hereinafter referred to as thiazolinethione, is known to be extremely useful in the photographic industry. For example, certain low molecular weight thiazolinethione compounds form light-sensitive silver complexes which are useful in coatings for photographic paper (Fr. Demande 2,019,578; Chem. Abstract., 74, 81769k (1971)). Derivatives of (I) have been disclosed to be useful when added to silver halide emulsions to enhance a black tone of an image and to increase the photosensitivity (Brit. 1,086,657; Chem. Abstr., 68, 17421q (1968)). Additional applications of thiazolinethiones in the photographic industry are as desensitizers for direct positive photography. Derivatives of (I), used as silver halide emulsion additives, were disclosed to exhibit more controlled coloring and contrast of photographic materials (Brit. Pat. No. 1,086,613; Chem. Abstr., 68, 17432u (1968); U.S. Pat. No. 3,367,779). Thiazolinethione compounds (I) have also been disclosed to be useful as emulsion additives to reduce fogging during the storage of photographic materials (Fr. Demande No. 2,019,603; Chem. Abstr., 74, 70255p (1971)) and to prepare photographic emulsions having low visible light sensitivity, high UV sensitivity, and low fog (Jpn. Kokai Tokkyo Koho JP No. 81,149,031; Chem. Abstr., 96, 226521q (1982)). However, utility of the thiazolinethione compounds is diminished in certain instances due to its capability of migrating among the layers in a photographic element.
The prior art has disclosed polymers which incorporate the thiazolinethione heterocycle as a pendant group. These have been obtained by copolymerizing N-vinylbenzothiazole-2-thione (II) or N-allylbenzothiazole-2-thione (III) with methyl methacrylate (M. A. Askarov, A. S. Bank, et al., J. Polym. Sci., Polym. Symp., No. 40, 199 (1973), Chem. Abstr., 80, 15393f (1974); Uzb. Khim. Zh., 56 (1976), Chem. Abstr., 85, 63891s (1976); Deposited Doc., VINITI, 529 (1976), Chem. Abstr., 88, 74774r (1978); Vysokomol Soedin., Ser. B., 19, 255 (1977), Chem. Abstr., 87, 24091c (1977)). The copolymers had greater light and heat stabilities than methyl methacrylate homopolymer. ##STR2## It is believed that the prior art does not teach the thiazolinethione heterocycle incorporated into the backbone of a polymer.